Manifold

ABSTRACT

A manifold system for an internal combustion engine, comprising a housing designed as a collecting manifold, which housing has two inlet openings and an outlet opening for connecting two outlets of an internal combustion engine to an exhaust gas system in regard to flow and at least one connection opening provided on the housing for connecting to an outer shell of a double-shell air-gap-insulated manifold, and comprising at least one air-gap-insulated manifold connected to the connection opening, which air-gap-insulated manifold has an inner shell having an inlet opening for connecting to an outlet of the internal combustion engine in regard to flow and having an outer shell, wherein all air-gap-insulated manifolds are completely formed from sheet metal and are structurally or geometrically identical and, on the housing, the size of a distance A2 between one of the two inlet openings and the outlet opening is between 30 mm and 300 mm or between 50 mm and 120 mm.

FIELD OF THE INVENTION

The invention relates to a manifold system for an internal combustion engine, comprising a housing designed as a collecting manifold, with two inlet openings and an outlet opening for fluidically connecting two outlets of an internal combustion engine to an exhaust gas system. A connection opening is provided on the housing for connecting to an outer shell of a double shell air gap insulated manifold. At least one air gap insulated manifold is connected to the connection opening, having an inner shell with an inlet opening for the fluidic connection to one outlet of the internal combustion engine and with an outer shell.

BACKGROUND OF INVENTION

By inlet opening, outlet opening or connection opening is meant the respective end of a pipe or a housing that is connected by means of further connection means, such as flanges or welded material, to another structural part leading further away.

A housing for an internal combustion engine configured as a collecting manifold with a plurality of exhaust gas conduits is already known from EP 1 914 401 A2, one end of which having an exhaust gas inlet opening can be connected to an outlet of the internal combustion engine and whose other end is connected to a collecting device having an exhaust gas outlet opening. At least one exhaust gas conduit is formed as a casting from the outlet of the internal combustion engine to the collecting device and at least one other exhaust gas conduit is formed as a constructed pipe or shell piece from the outlet of the internal combustion engine to the collecting device.

DE 39 25 802 A1 describes a casting for the connection of two outlets of the internal combustion engine to an exhaust gas system, serving as an adapter for two manifold pipes. The connection of further outlets to the exhaust gas system is done by separate manifold pipes, which are not connected to the casting.

According to DE 103 01 395 A1, a double-walled housing fashioned as a collecting manifold is known, in which the outer shell directly joins together all outlets of the internal combustion engine.

SUMMARY OF THE INVENTION

The present invention proposes to solve the problem of modifying an exhaust gas system so that the sound of the exhaust gas noise and thus the exhaust gas system is optimized across several important rpm ranges of the internal combustion engine. Each engine has its individual optimal operating points in which the complex relationship between torque and fuel consumption is advantageous. Such optimal operating points occur in relatively narrow rpm ranges, so that the solution approach is addressed to acoustically modifying the exhaust gas system in regard to these relevant rpm ranges.

The problem is solved according to the invention in that all air gap insulated manifolds are completely formed from sheet metal and are structurally or geometrically identical and the size of the distance on the housing between one of the two inlet openings and the outlet opening is between 30 mm and 300 mm or between 50 mm and 120 mm.

Thanks to the identical design of the air gap insulated manifold connected to the collecting manifold or the housing, an acoustics is accomplished between the outlet and the collecting pipe which sounds more harmonious than known manifold systems, especially in 6-cylinder inline engines. This improvement is especially beneficial when a definite size of the distance between one of the two inlet openings and the outlet opening exists, which varies between 50 mm and 120 mm, depending on the model of manifold system. In the case of short distances with the advantage of small design size, it has been found that the sonic behavior is already affected with slight changes in the distance. An increasing of the distance, on the other hand, produces advantageous sonic properties.

Such manifold systems will be used preferably in truck Diesel engines or stationary Diesel engines in which a turbocharger is arranged adjacent to the collecting manifold. The housing, fashioned as the central and load-bearing part, constitutes the necessary statics for the connecting of the turbocharger to the outlets on the engine housing.

It is especially advantageous for this when the distance is dimensioned as a function of sound waves of the exhaust gas whose wavelength is calculated in terms of n*A2 or 1/n*A2, n being an element of the natural numbers, but not zero. Here, A2 is the above described size of the distance between one of the two inlet openings and the outlet opening. L is the mean physical wavelength of sound, calculated from the quotient of the speed of propagation C [m/s=meters per second] of the sound in the exhaust gas and the frequency f[1/s=Hertz] of the wave. At an exhaust gas temperature of 700° C. and a frequency of 300 Hertz [Hz], one gets a wavelength of around 750 mm. This signal with 300 Hz is generated, for example, by a 6-cylinder engine at 3000 revolutions per minute [rpm]. This low-frequency signal would be accentuated with a distance of 1/10 of the wavelength, i.e., with a distance A2 of 75 mm in the housing.

It can also be advantageous for this if the two inlet openings within the housing stand in a fluidic and acoustic exchange with each other, which further enhances the harmonization, because a dynamic equalization can occur inside the housing.

Moreover, it can be beneficial if the two inlet openings are separated in the housing by a duct wall and two flow ducts are formed by the duct wall, wherein both flow ducts empty into the outlet opening at the end of the duct wall and the two flow ducts stand in fluidic and acoustic exchange via an opening or perforation provided upstream from the outlet opening in the duct wall. In this way, the properties of an absolute group separation without any acoustic and flow-dynamic interaction between the two manifold regions adjoining the flow ducts are coupled with the properties without group separation and with full acoustic and flow-dynamic interaction. The opening or perforation provided in the duct wall reduces the flow-dynamic interaction, but at the same time the acoustic interaction remains largely intact. The degree of the acoustic interaction varies both with the distance between one of the two inlet openings and the outlet opening and with the rpm, because the interaction decreases with increasing rpm depending on the size of the opening as a constrained leakage point.

It can also be beneficial if the opening or the perforation has an overall cross section between 25 mm² and 50 mm².

It can be advantageously provided that the collecting manifold or the housing is fashioned as a single-piece casting. The vibrational behavior of a casting is very advantageous compared to that of a sheet metal part, insofar as the acoustics of collecting manifolds is concerned.

It can be of special importance to the present invention when the collecting manifold is formed from a low-alloy gray cast iron with a carbon content of at least 1.00 wt. % and further alloy additions each with a mean content of not more than 50.00 wt. %. Such materials known as gray cast iron have a beneficial acoustic vibration behavior.

Alternatively, it can be advantageous when the housing is formed entirely of sheet metal, as a multiple piece and double-walled part, and also air gap insulated with an outer housing and an inner housing, the connection opening being provided on the outer housing. The acoustic disadvantages of sheet metal can be compensated by a special shaping of the outer housing.

It is also advantageous for the air gap insulated manifold to have a connection opening and an outlet opening, wherein the air gap insulated manifold is directly connected to the collecting manifold by its connection opening and is connected across its outlet opening to the connection opening of another air gap insulated manifold. In this way, one can both connect only one air gap insulated manifold to a collecting manifold on both sides and also connect two air gap insulated manifolds on both sides. The manifold system with two sheet metal manifolds for a 4-cylinder internal combustion engine can be supplemented with two additional and identical sheet metal manifolds and expanded into a manifold system for a 6-cylinder internal combustion engine.

It can be advantageous for this when the outlet opening of the outermost air gap insulated manifold is closed by a lid. The lid is adapted according to the particular system for each of the identical air gap insulated manifolds.

Moreover, it can be advantageous when the air gap insulated manifold is joined to the collecting manifold by a bonding technique, such as welding or soldering or gluing. In particular, the welded connection offers a very simple and economical fabrication method for a collecting manifold made of gray cast iron. For reasons of flexible installation it can also be advantageous to connect the air gap insulated manifold to the collecting manifold by form fitting with a union nut or a V-band clamp or a flange connection or a clamping element.

Moreover, it can be of advantage when the collecting manifold has only one connection opening by which two air gap insulated manifolds are connected directly or indirectly. This asymmetrical design has acoustic benefits over the symmetrical design for special applications.

Finally, it can be of advantage when the collecting manifold connects the outlet openings to a housing of a turbocharger and for this purpose forms a load-bearing structural part arranged between the engine block and the turbocharger.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the invention are explained in the patent claims and in the specification and represented in the figures. There are shown:

FIG. 1a , a sectional view of a housing fashioned as a collecting manifold with flow ducts standing in interaction;

FIG. 1b , a side view of the collecting manifold of FIG. 1 a;

FIG. 2, a sectional view of a manifold system with a collecting manifold with flow ducts standing in interaction and four air gap insulated manifolds;

FIG. 3, a sectional view of a manifold system with a collecting manifold with flow ducts standing in interaction and two air gap insulated manifolds;

FIG. 4, a double-wall collecting manifold made of sheet metal;

FIG. 5, a sectional view of a flange connection between collecting manifold and air gap insulated manifold;

FIG. 6, a sectional view of a connection between collecting manifold and air gap insulated manifold via an inlay in the collecting manifold;

FIG. 7a , a view of a collecting manifold with V-bank clamp arranged at both sides;

FIG. 7b , a sectional view of a V-bank clamp connection between collecting manifold and air gap insulated manifold;

FIG. 8a , a schematic representation of the distance between an inlet opening and the outlet opening in a collecting manifold as seen from above;

FIG. 8b , a schematic representation of the distance between an inlet opening and the outlet opening in a collecting manifold in side view.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a shows a sectional view of a housing 2 fashioned as a collecting manifold with flow ducts 25, 26 standing in interaction. The housing 2 is formed from a gray cast iron and in addition to two inlet openings 20, 21 for connecting the housing 2 to outlets (not represented) of an internal combustion engine it also has two connection openings 22, 23, each for an air gap insulated manifold 31, 32. From the two inlet openings 20, 21, two flow ducts 25, 26 arranged alongside each other and partly separated by a duct wall 27 extend inside the housing 2 up to an outlet opening 24 of the housing, represented in FIG. 1b . To improve the acoustic properties of the collecting manifold 2, the two flow ducts 25, 26 stand in interaction with each other across an opening 271 in the duct wall 27.

In the sample embodiment of a manifold system 1 shown in FIG. 2, the housing 2 is not symmetrical in design, but as in the sample embodiment of FIGS. 1a and 1b it has two connection openings 23 for one air gap insulated manifold 31, 32 apiece as well as the two inlet openings 20, 21. From the two inlet openings 20, 21, two flow ducts 25, 26 extend inside the housing 2 up to the outlet opening 24 of the housing 2. Here as well, the two flow ducts 25, 26 are partly separated in their interaction by a duct wall 27. The average length of the two flow ducts 25, 26 represented by arrows corresponds to a distance A2, more closely described in FIGS. 8a and 8b , between the respective inlet opening 20, 21 and the outlet opening 24. In this sample embodiment, the distances A2 differ by a factor of 1.6.

FIG. 3 shows a housing 2 for a manifold system 1 for an internal combustion engine with four cylinder arranged in line. The housing 2 has only one connection opening 22 for an air gap insulated manifold 30. In this housing 2, no reduction in the interaction between the two flow ducts 25, 26 by a duct wall 27 is provided.

FIG. 4 shows an air gap insulated housing 2, which is fashioned as a collecting manifold. The housing 2 has an outer housing 28 and two inner housings 29 integrated in the outer housing 28.

The housing 2 is fashioned as a load-bearing part and connects the outlets of the engine block (not represented) to a housing of a turbocharger (not represented). On one or both sides, air gap insulated manifolds 30-33 are connected to the housing 2, not having any load-bearing or statically relevant function.

The air gap insulated manifolds 30-33 represented in the two sample embodiments of FIGS. 2 and 3 are formed from sheet metal and are geometrically and structurally identical. Thanks to the identical shape of all air gap insulated manifolds 30-33, the acoustic properties at the most important operating points of the internal combustion engine are improved, because the vibration and resonance behavior is identical in all air gap insulated manifolds 30-33. A different configuration would have resulted in different vibration and resonance behavior.

Furthermore, the identical shape has the benefit that, in combination with a housing 2 formed as a collecting manifold 2 for two outlets, a manifold system 1 for a 4-cylinder internal combustion engine supplemented with two air gap insulated manifolds 30, 33 can be used for a 6-cylinder internal combustion engine. The last air gap insulated manifold 30, 33 in the series is closed by a lid 4. The connection between the air gap insulated manifolds 30-33 and between the lid 4 and the respective air gap insulated manifold 30, 33 is formed as a welded connection.

The identical air gap insulated manifolds 30 have an inner shell 34 and an outer shell 35 surrounding the inner shell 34. The two shells 34, 35 extend from a respective inlet opening 36 in the flow direction to a respective outlet opening 37 and contrary to the flow direction to a respective connection opening 38. At the respective openings 36-38, the inner shell 34 and the outer shell 35 are joined together flush in one of the flow directions.

When the respective air gap insulated manifold 30-33 is connected to the housing 2, the outer shell 35 is critical for the particular joining technique. As a rule, the inner shell 34 is only inserted into the housing 2.

The connection between the housing 2 and the outer shell 35 of the respective air gap insulated manifold 31, 32 is preferably formed as a welded connection. Alternatively to this, a connection as a flange 7 or inlay 8 or V-band clamp 6 is provided according to FIG. 5-7 b.

The distance A2 represented in FIGS. 8a and 8b between the respective inlet opening 20, 21 and the outlet opening 24 is also dependent on the size ratios of the respective diameter De of the inlet openings 20, 21 to the diameters Da of the outlet opening 24. For an optimal acoustic adaptation to the most important operating points of the internal combustion engine, especially in regard to the critical rpm for the most important load regions, the distances A2, the diameter ratios De, Da and the identical shape of the air gap insulated manifolds 30-33 are thus critical. 

What is claimed is:
 1. A manifold system for an internal combustion engine with a) a housing designed as a collecting manifold, with two inlet openings and an outlet opening for fluidically connecting two outlets of an internal combustion engine to an exhaust gas system, b) and at least one connection opening provided on the housing for connecting to an outer shell of a double shell air gap insulated manifold, as well as c) at least one air gap insulated manifold connected to the connection opening, having an inner shell with an inlet opening for the fluidic connection to one outlet of the internal combustion engine and with an outer shell, wherein d) all air gap insulated manifolds are completely formed from sheet metal and are structurally or geometrically identical and e) a size of a distance (A2) on the housing between one of the two inlet openings and the outlet opening is between 30 mm and 300 mm.
 2. The manifold system according to claim 1, wherein the distance (A2) is dimensioned as a function of sound waves of the exhaust gas whose wavelength (L) of sound is calculated by n*A2 or 1/n*A2, n being an element of natural numbers, but not zero.
 3. The manifold system according to claim 1, wherein the two inlet openings within the housing stand in a fluidic and acoustic exchange with each other.
 4. The manifold system according to claim 1, wherein the two inlet openings are separated in the housing by a duct wall and two flow ducts are formed by the duct wall, wherein both flow ducts empty into the outlet opening at the end of the duct wall and the two flow ducts stand in fluidic and acoustic exchange via an opening or perforation provided upstream from the outlet opening in the duct wall.
 5. The manifold system according to claim 4, wherein the opening or the perforation has an overall cross section between 25 mm² and 50 mm².
 6. The manifold system according to claim 1, wherein the housing is fashioned as a single-piece casting.
 7. The manifold system according to claim 6, wherein the housing is formed from a low-alloy gray cast iron with a carbon content of at least 1.00 wt. % and further alloy additions each with a mean content of not more than 50.00 wt. %.
 8. The manifold system according to claim 1, wherein the housing is formed entirely of sheet metal, as a multiple piece and double-walled part, and also air gap insulated with an outer housing and at least one inner housing, the connection opening being provided on the outer housing.
 9. The manifold system according to claim 8, wherein the air gap insulated manifold has a connection opening and an outlet opening, wherein the air gap insulated manifold is directly connected to the housing by its connection opening and is connected across its outlet opening to the connection opening of another air gap insulated manifold.
 10. The manifold system according to claim 9, wherein the outlet opening of the outermost air gap insulated manifold is closed by a lid.
 11. The manifold system according to claim 1, wherein the air gap insulated manifold is joined to the housing by a bonding technique.
 12. The manifold system according to claim 1, wherein the housing has only one connection opening by which two air gap insulated manifolds are connected directly or indirectly.
 13. The manifold system according to claim 1, wherein the housing connects the outlet openings to a housing of a turbocharger and for this purpose forms a load-bearing structural part arranged between an engine block and the turbocharger.
 14. A system consisting of a manifold system according to claim 1 and an internal combustion engine.
 15. The manifold system according to claim 2, wherein the two inlet openings within the housing stand in a fluidic and acoustic exchange with each other.
 16. The manifold system according to claim 1, wherein the size of the distance (A2) on the housing between one of the two inlet openings and the outlet opening is between 50 mm and 120 mm.
 17. The manifold system according to claim 11, wherein the bonding technique is welding, soldering, or gluing.
 18. The manifold system according to claim 2, wherein the two inlet openings within the housing stand in a fluidic and acoustic exchange with each other; wherein the two inlet openings are separated in the housing by a duct wall and two flow ducts are formed by the duct wall, wherein both flow ducts empty into the outlet opening at the end of the duct wall and the two flow ducts stand in fluidic and acoustic exchange via an opening or perforation provided upstream from the outlet opening in the duct wall; and wherein the opening or the perforation has an overall cross section between 25 mm² and 50 mm².
 19. The manifold system according to claim 18, wherein the housing is fashioned as a single-piece casting; wherein the housing is formed from a low-alloy gray cast iron with a carbon content of at least 1.00 wt. % and further alloy additions each with a mean content of not more than 50.00 wt. %.
 20. The manifold system according to claim 19, wherein the air gap insulated manifold is joined to the housing by a bonding technique; wherein the housing has only one connection opening by which two air gap insulated manifolds are connected directly or indirectly; and wherein the housing connects the outlet openings to a housing of a turbocharger and for this purpose forms a load-bearing structural part arranged between an engine block and the turbocharger. 